When people who are not experts in robotics first encounter a robot they may be excited and curious but usually have no idea what the robot can and will do. For example, when a mobile robot moves around in a human living environment, people may act cautiously and nervously around it mainly because they do not know what the robot will do next and they feel the need to prepare themselves for its sudden and unexpected movements. They may observe the robot carefully and use their cognition systems to make sense of its motions and predict its intentions. Unfortunately, there typically is not a clear indication of the robot's next move, and the programming built into the robot is not observable by people who cohabitate with it. The direction in which a robot will turn is not obvious by looking at it, and it is typically not possible to know if it will speed up or slow down, or if it will stop or proceed to run over an object. Without knowing what a robot will do next, humans cannot act appropriately and collaboratively with the robot. If those persons could know the intention of the robot and its next move at all times, they would feel much more comfortable and at ease around them.
Communication between humans and robots holds the key to building a human-robot synergic relationship. Humans can collaborate efficiently since they have the ability to make judgments about the intentions of others as they listen to others' auditory expression and witness them in action. Humans rely upon intention perception to understand the current actions of others and predict their next moves and decide what their own action should be in an attempt to synchronize and influence the actions of others. In the context of a mobile robot, a human not only must understand the current motion of the robot but also must perceive the robot's intention in order to predict its next move so as to actively collaborate with the robot and create synergy.
One approach to enable such communication is to design robots that can express themselves as humans do so that humans can identify the robot's intentions as they observe them in action (as humans do with other humans). However, it is unrealistic to require all the robots coexisting with humans to have human-like appearance, kinematics, and dynamics. A robot's motion, by nature, is far different from regular human motion. The motions humans consider to be unnatural are rooted in the physical properties and configurations of robots. A robot's material, actuators, and sensors are fundamentally different from humans, and yield rather different patterns of acceleration, deceleration, and the like. A robot is designed to amplify its strengths and efficiently perform certain tasks. These differences provide robots with abilities that humans do not have, such as super speed and extreme precision. Moreover, human-like robotic manipulators do not always move as human arms because the manipulators have different kinematics and ranges of motion. For example, a typical robotic wrist has a large rolling motion (close to 360 degrees) and the human wrist can only roll between approximately 90 and 180 degrees. Although limiting a robot's wrist motion to make it more human-like could help humans anticipate its movements, it would also significantly reduce the robot's capability and, at least in part, defeat the purpose of utilizing a robot to perform the task.
In view of the above discussion, it can be appreciated that it would be desirable to have means for enabling humans to better anticipate actions of a robot.